Electric incandescent lamp mount structure



March 24, 1970 F. A. MOSBY ELECTRIC INCANDESCENT LAMP MOUNT STRUCTUREFiled April 10, 1968 Irv/an hor: Frederick AMosbg y aw His Atto negUnited States Patent M US. Cl. 3l3278 2 Claims ABSTRACT OF THEDISCLOSURE A mount structure for a coiled-coil filament, singleendedlamp (especially of the halogen cycle type) wherein the coiled-coil issupported by a shorter lead wire connected securely to a coiled leg atthe lower end of the coiled-coil, and to a longer lead wire whichextends through the interior of the coiled-coil and is secured to acoiled leg at the upper end of the coiled-coil. The two lead wires aredisplaced longitudinally to slightly stretch the coiled-coil to avoidsagging of the turns during operation, and the relative positions of thelead wires are maintained by an insulating bridge interconnecting them.

The invention relates generally to electric incandescent lamps, and moreparticularly to mount structures therefor. The invention is particularlyuseful in lamps of the compact halogen cycle type, and especially suchlamps of the single-ended type and having a coiled-coil filamentextending longitudinally of the enclosing envelope or bulb.

In accordance with one object of the invention, the mount structure issuch as to make it possible to prestretch the coiled-coil filamentbefore it is sealed into the envelope.

Accordingly, the filament is supported by rigid respective short'andlong lead-in wires which are secured to the lower and upper ends of thefilament, with the long leadin wire jextending through the interior ofthe coiled-coil filament. The said long lead-in wire is preferably of arefractory metal like tungsten and is of such size as to maintain itsrigidity despite the current flow therethrough and despite the intenseheat of the enclosing coiled-coil filament.

The drawing is an elevation of a lamp comprising the invention.

Referring to the drawing, the lamp has a mount structure including acoiled-coil tungsten filament 1, short and long tungsten inner leadwires 2 and 3 respectively, and a bridge member comprising an insulatingrod portion 4 which may be made of so-called hard glass of high meltingpoint, or of fused silica or quartz.

As illustrated herein, the shorter lead wire 2 has its upper endenclosed in, and preferably welded to, a singlecoiled lower leg portion5 of the filament and which extends downward from the rim of thecoiled-coil body portion 1 of the filament. The longer lead wire 3 hasits lower portion parallel to the shorter lead wire 2, and its upperportion offset at 6 to be substantially in the axis of the coiled-coil1, with its upper end enclosed in, and preferably welded to, an uppersingle-coiled leg 7 of the filament. The mount structure, and moreparticularly the lead-in conductors, further include inter- 3,502,931Patented Mar. 24, 1970 mediate seal portions 8 which are preferablyextremely thin foils of molybdenum for sealing into fused silica, andouter lead wire portions 9 which may be of molybdenum.

As further illustrated by way of example, the bridge member 4 mayinclude short coils 10 each having one end secured in one end of thebridge 4, and each enclosing and secured to portions of respective innerlead wires 2 and 3, preferably by welding. Before the coil portions 10are secured to the lead wires 2 and 3, the said lead wires are displacedlongitudinally relative to one another to stretch the coiled-coil 1sufficiently so that adjacent turns thereof do not sag and touch eachother when they are at operating temperature. The stretch or tension inthe coiled-coil 1 is thereafter maintained by virtue of the bridge 4, 10which holds the lead wires 2 and 3 in place.

The mount structure thus far described is sealed into an envelope 11which may be of tubular fused silica or quartz glass and which has beenpreviously tubulated by inserting an end of an exhaust tube of fusedsilica, indicated by dotted lines at 12, into the end of the envelope 11and then forming a flattened pinch seal 13 which seals that end of theenvelope except for the exhaust tube 12 which is hermetically sealed inthe pinch but is maintained open through the said pinch seal 13 in knownmanner.

The preassembled mount structure is then inserted into the envelope 11,preferably with the upper ends of lead wire 3 and filament leg 7extending into the cavity at 14 formed by the enclosed portion of theexhaust tube. The other (lower) end of the envelope 11 is then heatedand pinch sealed at 15 to hermetically seal the foils 8 therein, withadjacent portions of inner leads 2; and 3 and outer leads 9, 9 alsoembedded in the pinch seal 15.

The envelope 11 is then exhausted and filled through exhaust tube 12with the desired inert gas, such as nitrogen, argon krypton or xenon ormixtures thereof, and a small amount of the desired halogen such asiodine or bromine or compounds thereof, the bromine in particular beingpreferably introduced as a compound such as hydrogen bromide or ahydrocarbon of bromine. The envelope is then sealed off by heating andtipping off the exhaust tube 12 at a point close to the pinch seal 13,as indicated by the sealed tip 16.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electric incandescent lamp, a mount structure comprising ahelically coiled-coil filament adapted to be vertically disposed andhaving a single-coiled upper leg extending upwardly away from thecoiled-coil substantially along the axis thereof and a single-coiledlower leg extending downwardly away from the rim of the coiledcoil andparallel to its axis, a shorter lead wire having its upper end disposedwithin said lower filament leg and securely attached thereto, a longerlead wire having its lower portion generally parallel to said shortedlead and its upper portion offset toward the axis of the coiled-coil andextending through the interior of the coiled-coil along its axis andinto the said coiled upper leg to which it is securely attached, saidshorter and longer lead wires being displaced longitudinally in oppositedirections so that the coiled-coil is held thereby in a stretchedcondition, and an insulating bridge member extending between saidshorter and longer lead wires and securely attached thereto andmaintaining the relative longitudinal positions of said shorter andlonger lead Wires and the stretched condition of the coiled-coil.

2. A lamp as set forth in claim 1, including a tubular bulb of vitreousmaterial enclosing said mount structure with its axis substantiallycoincident with the axis of said coiled-coil, a pressed seal portion atthe bottom of said envelope hermetically sealing extensions of saidshorter and longer lead wires, and a cavity in the closed upper endportion of said envelope into which extends the uppermost ends of saidfilament upper leg and the portion of longer lead wire enclosed thereby.

References Cited UNITED STATES PATENTS 2,565,138 8/1951 Leighton 313-278RAYMOND F. HOSSFELD, Primary Examiner U.S. c1. X.R.

